Mats of multifilament glass strands of indeterminate length randomly disposed and bonded to each other which have heretofore been used as reinforcement for organic resins and polymers have been characterized by the use as binders of a combination of emulsified polymer or resin and powdered solid polymer or resin. The present invention comprehends the discovery that in using mats of this type for reinforcing thermoplastic resins and polymers, and especially polyamides, as stampable laminates, it is advantageous to use a binder which material omits the powdered solid as a component of the mat binder and also to use a particular composition for sizing the individual glass filaments making up the strands of which the mat is formed.